Packet communication systems and their use through which to communicate have become pervasive in modern society. A packet communication system, similar to other types of communication systems, provides for the communication of data between communication stations of a set of communication stations. The set includes at least a sending station and a receiving station. Data originated at, or otherwise provided to, a sending station is caused to be communicated by the sending station for delivery at a receiving station. The data sent by the sending station is sent upon a communication channel, and the receiving station monitors the communication channel, thereby to detect delivery of the data communicated thereon.
In a packet communication system, data that is communicated is first packetized into packets of data, and the data packets, once formed, are then communicated, sometimes at discrete intervals. Once delivered to a receiving station, the information content of the data is ascertained by concatenating the information parts of the packets together. Packet communication systems generally make efficient use of communication channels as the communication channels need only to be allocated pursuant to a particular communication session only for the period during which the data packets are communicated. Packet communication channels are sometimes, therefore, shared communication channels that are shared by separate sets of communication stations between which separate communication services are concurrently effectuated.
Operating specifications that define the operating protocols of various types of packet radio communication systems have been promulgated and yet others are undergoing development and standardization. A packet radio communication system provides the advantages of a radio communication system in that the communication stations that are parties to a communication session need not be interconnected by electrically-conductive connectors. Instead, the communication channels of a packet radio communication system are formed of radio channels, defined upon a portion of the electromagnetic spectrum.
While packet radio communication systems have been developed for the effectuation of various different types of communication services, much recent interest has been directed towards the development of packet radio communication systems capable of providing for data-intensive communication services. For instance, the IEEE 802.15.3a operating specification contemplates an OFDM (Orthogonal Frequency Division Multiplexed) UWB (Ultra Wide Band) communication system, capable of communicating data over wide bandwidths over short ranges.
A structured data format is set forth in the present promulgation of the operating specification. The data format of a data packet formed in conformity with the IEEE 802.1 5.3a includes a preamble part and a payload part. Other packet communication systems analogously generally format data into packets that also include a preamble part and a payload part. The payload part of the packet contains the information that is to be communicated. That is to say, the payload part is nondeterminative. Conversely, the preamble part of the data packet does not contain the informational content that is to be communicated but, rather, includes determinative data that is used for other purposes. And, in particular, the preamble part of an IEEE 802.15.3a packet preamble includes three parts, a packet sync sequence, a frame sync sequence, and a channel estimation sequence. The packet sync sequence is of a length of twenty-one OFDM (symbols): the frame sync sequence is of a length of three OFDM symbols, and the channel estimation sequence is of a length of six OFDM symbols. And, collectively, the sequences are of a time length of 9,375 microseconds.
The preamble portions are used, for instance, to facilitate synchronization between the sending and receiving stations that send and receive the data packet, respectively. Additionally, the preamble is used for purposes of automatic gain control (AGC). For use of automatic gain control, a receiving station is able to set its gain at an appropriate level, e.g., to facilitate application of received data to an analog-to-digital converter to supply useful bits to a baseband part of the receiving station. The preamble is further used for purposes of packet detection. Packet detection identifies to the receiving station the reception at the receiving station of the packet. Upon detection of the packet, e.g., various state machines at the receiving station are started to enable processing of the incoming packet. And, of particular significance herein, the preamble also is used for channel estimation. The radio channel upon which the packet is communicated undergoes reflections and is otherwise distorted during its communication to the receiving station. To receive the transmitted data correctly, the receiving station must be provided with a good estimate of the channel to permit proper compensation to be made of the channel.
The sequences of which the preamble is formed preferably exhibit good peak-to-average ratios to ensure best that the sequences are not truncated, i.e., clipped when passed through sending and receiving station circuitry. While existing proposals for values of such sequences have been set forth, if a manner could be provided by which to identify and use sequences that exhibit improved peak-to-average ratios, improved communication system performance would be possible.
It is in light of this background information related to communications in a packet communication system that the significant improvements of the present invention have evolved.